An ideal scaffold should have good mechanical properties and provide a biologically functional implant site. A rapid prototyping system has been introduced as a good method of fabricating 3D scaffolds that mimic the structure in the human body. However, the scaffolds have strands that are too smooth and a pore size that is too large relative to the seeded cells and present unfavorable conditions for initial cell attachment. To overcome these problems, we propose a hybrid technology combining a 3D rapid prototyping system and an electrospinning process to produce a hierarchical 3D biomedical scaffold. The resulting structure consists of alternating layers of 3D‐structured/microsized polymer strands and nanofiber webs. The results of cell culturing of chondrocytes indicate that this technique is a feasible new method for fabricating high quality 3D polymeric scaffolds.magnified image

Nanofibers are widely used in a range of material applications, such as filter media, biosensors, military protective coatings, three‐dimensional tissue scaffolds, composites, drug delivery, wound dressings and electronic devices. To fabricate nanofibers with desired physical and chemical functions, a variety of electrospinning processes have been introduced using specially designed collectors, microelectromechanical system (MEMS) nozzle tips and auxiliary electrodes to stabilize the spin jets. However, the development of new electrospinning processes continues in the search for ‘tailor‐made’ nanofibers, in which parameters such as the fiber orientation and three‐dimensional structure are ultimately controllable. This paper discusses recently suggested electrospinning methods that are designed to impart specific functionality. It also details the correlations between applied processing parameters and the obtained physical properties of electrospun fibers. Finally, future design directions are suggested for developing an electrospinning apparatus capable of producing optimally structured nanofibers. Copyright © 2007 Society of Chemical Industry

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The extreme light infrastructure attosecond light pulse source offers beamtime for users of various attosecond and particle sources driven by versatile laser systems. Here we report on the state of the art of a few-cycle, multi-TW, 1kHz repetition rate laser system, now fully operational in the facility. The system is based on four stages of optical parametric amplifiers (OPAs) pumped by a total of 320mJ, 80ps frequency-doubled Nd:YAG laser pulses. All OPA stages utilize double crystal configuration, which design has been also confirmed by model calculations. The 1kHz SYLOS 2 system produces 32mJ laser pulses around a central wavelength of 891nm with 6.6fs (<2.3 optical cycles) pulse duration exceeding the peak power of 4.8 TW on a daily basis. The recorded best pulse duration is 6.3fs, which corresponds to 2.12 cycles and 5.1 TW peak power. During long-term (24h) performance tests, energy stability of 1.2%, carrier-envelope phase (CEP) stability of 210mrad, and pointing stability of 0.4µrad were demonstrated, while the Strehl ratio of the beam is kept above 0.75. In order to help the alignment of all the different experiments at the facility and to reduce the workload on SYLOS 2 system, a second laser system has been developed. The so-called SYLOS Experimental Alignment (SEA) laser mimicks the performance of the SYLOS 2 laser, but at a repetition rate two orders of magnitude lower and without CEP-stabilization. The three single-crystal OPA stages of the SEA laser provide 42mJ pulse energy for the users, while having energy stability of 0.87% and sub-13fs pulse duration at a repetition rate ranging from a single shot up to 10Hz.

Cover: The image shows a hybrid polymeric scaffold that was fabricated using a rapid prototyping (RP) method and electrospinning process. The panels clearly indicate that the layers of electrospun micro-/nanofibers are located between the layers of dispensed poly("-caprolactone) strands. Further details can be found in the article by